You can only infer a little from oil color, bit the clearer the better obviously. The new 300 engines are great, the canister style oil filter really helps keep the oil clean and extend engine life. The 1.5l capacity refers to engine rebuild, you won't eve get every drop out unless your rebuilding. Last time I did an oil change w/filter (which you should change every time) it took more than 1.3l. I'll picky about getting as much dirty oil out as possible, warming the bike up, tipping it from right to left to get the oil to the drain bolt, and being patient and letting it drip until it won't anymore. So a good starting point, put 1.3l in and measure. Most likely you will have to add a tad bit.
